A. Field of the Invention
This invention relates to a movable disk printer and in one of its aspects to such a printer in which printing is provided while a movable carriage on which the movable disk is mounted and the movable disk is on the fly. In another aspect of this invention, it relates to such a printer in which the velocity of the carrier when moving between adjacent positions is variable, and the force applied to cause printing is varied according to the specific character being printed. In this respect this invention is a specific improvement upon the printing apparatus and methods disclosed in U.S. Pat. No. 4,030,591, assigned to the assignee of this invention, which disclosure is specifically incorporated herein by reference.
B. Description of the Prior Art
Printers which utilize a rotating disk with characters on the periphery thereof are well known. Several such printers are commercially available. Rotating disk printers can be divided in categories by either focusing on how the disk rotates or by focusing on how the carrier traverses.
Focusing on how the disk rotates, such printers can be divided into a first category where the disk constantly rotates and into a second category where the motion of the disk is intermittent. In printers with a constantly rotating disk, printing takes place when the hammer strikes the rotating disk. Rotation of the disk is not stopped each time a character is printed. In printers with a disk that intermittently rotates, the disk is rotated to the desired print position and then stopped. There is no disk rotation while printing takes place.
An alternate division of disk printers can be made by focusing upon the motion of the carrier. In some printers, the traverse of the carrier is stopped each time printing takes place. In other printers the carrier is moving at the instant when printing occurs. In both the type where the carrier is moving when printing occurs and in the type where the carrier is stopped when printing occurs, the disk may or may not be rotating at the time of printing. In some printers where the carrier is moving at a fixed speed when printing takes place, the carrier is slowed down and stopped between print positions in order to give the rotating disk time to move to the desired character.
In U.S. Pat. No. 4,030,591, a number of issued and pending patents are discussed which relate generally to printers of the type discussed above. As pointed out in this discussion, none of the references discussed show a printer where the carrier is moving at a plurality of different speeds when printing occurs and where the firing of the print hammer is timed dependent upon the speed of the carrier at the particular time. That specific feature, which permits increased printing speed, is found in U.S. Pat. No. 4,030,591, and is also one of the feature of this invention. However, the apparatus in that patent does not incorporate apparatus for varying the striking force of the hammer which is necessary in order to achieve high print quality.
In U.S. Pat. No. 3,858,509, issued to Willy J. Grundherr, a rotating disk printing apparatus is disclosed in which the striking force applied to the hammer can be varied between "light" and "hard". However, in that patent the printing is not done on the fly and there is no need to coordinate the speed of the carriage and the travel time of the print hammer to insure that the position of the character to be printed is at the print impact point at the time it is caused to strike the printing medium.